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Title: TU-H-CAMPUS-TeP2-04: Measurement of Stereotactic Output Factors with DNA Double-Strand Breaks

Abstract

Purpose: Radiotherapy treatment is specified by radiation dose prescriptions, but biological DNA damage actually controls treatment effectiveness. It is impractical to directly measure dose in the clinic, so we measure quantities, such as collected charge, and calculate the relationship to dose. At small fields, such as those in stereotactic radiosurgery (SRS), charged-particle equilibrium (CPE) breaks down and the accuracy of the measurement for delivered dose decreases. By measuring DNA double-strand breaks (DSB) directly, we believe treatment accuracy could improve by providing a more meaningful measurement. Methods: A DNA dosimeter, consisting of magnetic streptavidin beads attached to 4 kilobase pair DNA strands labeled with biotin and fluorescein amidite (FAM) on opposing ends, was suspended in phosphate-buffered saline (PBS). Twenty µL samples were placed in plastic micro-capillary tubes inside a water tank setup and irradiated with 10 cm, 3 cm, 1.25 cm, 0.75 cm, and 0.5 cm radiation field sizes, where the three smallest sizes were cones. After irradiation, the dosimeters were mechanically separated into beads (intact DNA) and supernatant (broken DNA/FAM) using a magnet. The fluorescence was read and the probability of DSB was calculated. This was used to calculate the output factor for an SRS beam and compared to thatmore » measured using a diode detector. Results: The output factors relative to a 10 cm field were 0.89±0.07, 0.76±0.08, 0.59±0.04, and 0.78±0.12 for the field sizes of 3 cm, 1.25 cm, 0.75 cm, and 0.5 cm, respectively. Some of the diode measurements do not fall within these uncertainties. Conclusion: This was the first attempt to measure output factors in a water tank with the DNA dosimeter. Although differences compared to the diode were observed, the uncertainty analysis ignored systematic errors. For future work, we will repeat this experiment to quantify and correct systematic errors, such as those caused by positional alignment and sample contamination. This work was funded in part by CPRIT (RP140105).« less

Authors:
; ; ; ; ; ; ; ; ; ; ;  [1]
  1. University of Texas HSC SA, San Antonio, TX (United States)
Publication Date:
OSTI Identifier:
22654068
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; CHARGED PARTICLES; DOSEMETERS; LEAD SULFIDES; RADIATION DOSES; STRAND BREAKS

Citation Formats

Cline, K, Obeidat, M, Stathakis, S, Kabat, C, Markovic, M, Papanikolaou, N, Rasmussen, K, Gutierrez, A, Ha, C, Lee, S, Shim, E, and Kirby, N. TU-H-CAMPUS-TeP2-04: Measurement of Stereotactic Output Factors with DNA Double-Strand Breaks. United States: N. p., 2016. Web. doi:10.1118/1.4957692.
Cline, K, Obeidat, M, Stathakis, S, Kabat, C, Markovic, M, Papanikolaou, N, Rasmussen, K, Gutierrez, A, Ha, C, Lee, S, Shim, E, & Kirby, N. TU-H-CAMPUS-TeP2-04: Measurement of Stereotactic Output Factors with DNA Double-Strand Breaks. United States. doi:10.1118/1.4957692.
Cline, K, Obeidat, M, Stathakis, S, Kabat, C, Markovic, M, Papanikolaou, N, Rasmussen, K, Gutierrez, A, Ha, C, Lee, S, Shim, E, and Kirby, N. Wed . "TU-H-CAMPUS-TeP2-04: Measurement of Stereotactic Output Factors with DNA Double-Strand Breaks". United States. doi:10.1118/1.4957692.
@article{osti_22654068,
title = {TU-H-CAMPUS-TeP2-04: Measurement of Stereotactic Output Factors with DNA Double-Strand Breaks},
author = {Cline, K and Obeidat, M and Stathakis, S and Kabat, C and Markovic, M and Papanikolaou, N and Rasmussen, K and Gutierrez, A and Ha, C and Lee, S and Shim, E and Kirby, N},
abstractNote = {Purpose: Radiotherapy treatment is specified by radiation dose prescriptions, but biological DNA damage actually controls treatment effectiveness. It is impractical to directly measure dose in the clinic, so we measure quantities, such as collected charge, and calculate the relationship to dose. At small fields, such as those in stereotactic radiosurgery (SRS), charged-particle equilibrium (CPE) breaks down and the accuracy of the measurement for delivered dose decreases. By measuring DNA double-strand breaks (DSB) directly, we believe treatment accuracy could improve by providing a more meaningful measurement. Methods: A DNA dosimeter, consisting of magnetic streptavidin beads attached to 4 kilobase pair DNA strands labeled with biotin and fluorescein amidite (FAM) on opposing ends, was suspended in phosphate-buffered saline (PBS). Twenty µL samples were placed in plastic micro-capillary tubes inside a water tank setup and irradiated with 10 cm, 3 cm, 1.25 cm, 0.75 cm, and 0.5 cm radiation field sizes, where the three smallest sizes were cones. After irradiation, the dosimeters were mechanically separated into beads (intact DNA) and supernatant (broken DNA/FAM) using a magnet. The fluorescence was read and the probability of DSB was calculated. This was used to calculate the output factor for an SRS beam and compared to that measured using a diode detector. Results: The output factors relative to a 10 cm field were 0.89±0.07, 0.76±0.08, 0.59±0.04, and 0.78±0.12 for the field sizes of 3 cm, 1.25 cm, 0.75 cm, and 0.5 cm, respectively. Some of the diode measurements do not fall within these uncertainties. Conclusion: This was the first attempt to measure output factors in a water tank with the DNA dosimeter. Although differences compared to the diode were observed, the uncertainty analysis ignored systematic errors. For future work, we will repeat this experiment to quantify and correct systematic errors, such as those caused by positional alignment and sample contamination. This work was funded in part by CPRIT (RP140105).},
doi = {10.1118/1.4957692},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}